Reading an integer from user input

Question

What I am looking for is how to read an integer that was given by the user from the command line  console project   I primarily know C   and have started down the C  path  I know that Console ReadLine    only takes a char string  So in short I am looking for the integer version of this    Just to give you an idea of what I m doing exactly   Console WriteLine  1  Add account     Console WriteLine  Enter choice      Console ReadLine       Needs to take in int rather than string or char    I have been looking for quite a while for this  I have found a lot on C but not C   I did find however a thread  on another site  that suggested to convert from char to int  I m sure there has to be a more direct way than converting

User · Answer

You could just go ahead and try        Console WriteLine  1  Add account         Console WriteLine  Enter choice          int choice int Parse Console ReadLine       That should work for the case statement   It works with the switch statement and doesn t throw an exception

User · Answer

You could create your own ReadInt function  that only allows numbers  this function is probably not the best way to go about this  but does the job  public static int ReadInt                 string allowedChars    quot 0123456789 quot            ConsoleKeyInfo read   new ConsoleKeyInfo            List lt char gt  outInt   new List lt char gt              while   read Key    ConsoleKey Enter  amp  amp  outInt Count  gt  0                         read   Console ReadKey true               if  allowedChars Contains read KeyChar ToString                                   outInt Add read KeyChar                   Console Write read KeyChar ToString                               if read Key    ConsoleKey Backspace                                if outInt Count  gt  0                                        outInt RemoveAt outInt Count - 1                       Console CursorLeft--                      Console Write  quot   quot                        Console CursorLeft--                                                    Console SetCursorPosition 0  Console CursorTop   1           return int Parse new string outInt ToArray

User · Answer

You need to typecast the input  try using the following   int input   Convert ToInt32 Console ReadLine        It will throw exception if the value is non-numeric   Edit  I understand that the above is a quick one  I would like to improve my answer   String input   Console ReadLine    int selectedOption  if int TryParse input  out selectedOption           switch selectedOption                      case 1                     your code here                   break             case 2                    another one                  break                 and so on  default               else          print error indicating non-numeric input is unsupported or something more meaningful

User · Answer

int op   0  string in   string Empty  do       Console WriteLine  enter choice        in   Console ReadLine      while   int TryParse in  out op

User · Answer

Better way is to use TryParse   Int32  userInput  if Int32 TryParse  Console Readline    out  userInput      do the stuff on userInput

User · Answer

You can convert the string to integer using Convert ToInt32   function  int intTemp   Convert ToInt32 Console ReadLine

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I didn t see a good and complete answer to your question  so I will show a more complete example   There are some methods posted showing how to get integer input from the user  but whenever you do this you usually also need to    validate the input  display an error message if invalid input is given  and   loop through until a valid input is given    This example shows how to get an integer value from the user that is equal to or greater than 1  If invalid input is given  it will catch the error  display an error message  and request the user to try again for a correct input   static void Main string   args                int intUserInput   0          bool validUserInput   false           while  validUserInput    false                        try               Console Write  Please enter an integer value greater than or equal to 1                    intUserInput   int Parse Console ReadLine       try to parse the user input to an int variable                             catch  Exception        catch exception for invalid input               if  intUserInput  gt   1    check to see that the user entered int  gt   1                 validUserInput   true                else   Console WriteLine  Invalid input                    end while          Console WriteLine  You entered     intUserInput           Console WriteLine  Press any key to exit             Console ReadKey           end main   In your question it looks like you wanted to use this for menu options   So if you wanted to get int input for choosing a menu option you could change the if statement to  if    intUserInput  gt   1   amp  amp   intUserInput  lt   4      This would work if you needed the user to pick an option of 1  2  3  or 4

User · Answer

I would suggest you use TryParse   Console WriteLine  1  Add account     Console WriteLine  Enter choice      string input   Console ReadLine    int number  Int32 TryParse input  out number     This way  your application does not throw an exception  if you try to parse something like  1q  or  23e   because somebody made a faulty input   Int32 TryParse returns a boolean value  so you can use it in an if statement  to see whether or not you need to branch of your code   int number  if  Int32 TryParse input  out number          no  not able to parse  repeat  throw exception  use fallback value      To your question  You will not find a solution to read an integer because ReadLine   reads the whole command line  threfor returns a string  What you can do is  try to convert this input into and int16 32 64 variable   There are several methods for this    Int Parse   Convert ToInt   Int TryParse     If you are in doubt about the input  which is to be converted  always go for the TryParse methods  no matter if you try to parse strings  int variable or what not   Update In C  7 0 out variables can be declared directly where they are passed in as an argument  so the above code could be condensed into this   if Int32 TryParse input  out int number           Yes input could be parsed and we can now use number in this code block        scope      else          No  input could not be parsed to an integer        A complete example would look like this   class Program       static void Main string   args                Console WriteLine  Hello World             var foo   Console ReadLine            if  int TryParse foo  out int number1                 Console WriteLine    number1  is a number                      else                       Console WriteLine    foo  is not a number                      Console WriteLine   The value of the variable  nameof number1   is  number1             Console ReadLine              Here you can see  that the variable number1 does get initialized even if the input is not a number and has the value 0 regardless  so it is valid even outside the declaring if block

User · Answer

Try this it will not throw exception and user can try again           Console WriteLine  1  Add account             Console WriteLine  Enter choice              int choice   0          while   Int32 TryParse Console ReadLine    out choice                         Console WriteLine  Wrong input  Enter choice number again

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I used int intTemp   Convert ToInt32 Console ReadLine     and it worked well  here s my example           int balance   10000          int retrieve   0          Console Write  Hello  write the amount you want to retrieve              retrieve   Convert ToInt32 Console ReadLine

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Use this simple line   int x   int Parse Console ReadLine

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static void Main string   args                Console WriteLine  Please enter a number from 1 to 10            int counter   Convert ToInt32 Console ReadLine               Here is your variable         Console WriteLine  The numbers start from            do                       counter                Console Write counter                     while  counter  lt  100            Console ReadKey

[c#] Reading an integer from user input

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